The present invention is directed to a bicycle computer and, more particularly, to a bicycle computer that can be used to shift a bicycle transmission based on the pedaling force applied by the rider.
Recently, the greater usefulness of bicycles has been increasingly recognized. Also, bicycle sports have fostered the automation of gear shifting in such bicycles, and the lower cost of microcomputers has increased the practical use of such automated bicycle gear shifters.
One type of electronic gear shifting device is disclosed in EP 0 529664A2. Here, the rider presses a button corresponding to a desired gear, and an electric motor positions the bicycle transmission in the selected gear.
A more advanced, automatic gear shifting device is disclosed in U.S. Pat. No. 5,213,548. This device detects the actual gear ratio based on the ratio between the crank speed and the bicycle speed and automatically shifts gears in accordance with a program when the crank is slow and the bicycle speed is fast.
In the technique disclosed in Japanese Laid-Open Patent Application 8-113181, the most suitable shift stage is selected depending on the bicycle speed and acceleration.
In order to properly shift the bicycle transmission, shifting must be done in response to the tensile force of the chain. Unfortunately, the above devices are unable to meet this requirement. For example, in JP 8-113181 the bicycle acceleration and the chain tensile force do not correspond to each other in a 1-to-1 manner. When one is riding uphill or is subject to greater wind pressure as the speed increases, there is no correlation between the acceleration of the bicycle chassis and the crank shaft torque which is proportional to the pedaling force of the feet, that is, the chain tensile force which is proportional thereto. As a result, acceleration data in itself is an inadequate, and even unusable, basis for achieving such control.
There is also a need to develop a bicycle gear shifter allowing the mechanical components of the shift mechanism to be operated under lower loads. The desired bicycle gear shifter should have a short operating delay time and should allow gears to be shifted in a short period of time under continuous low load conditions.